1. Field of the Invention
The invention relates to an apparatus for degassing and heating water by means of steam, essentially comprising a column with packing bodies arranged therein, with a distributor arranged at the column head for the water to be degassed, with a water supply line arranged upstream (at the head) of the column, with a water outlet line arranged downstream (at the bottom) of the column, and also a steam supply line and a venting line for the gas/steam mixture to be exhausted, the four lines opening into housings which are connected above and below the preferably cylindrical column to the latter.
Such apparatuses can be used in power station construction, in particular for degassing the feed water. In modern power station systems, particularly in the case of the combined cycle types, the consumption of treated water is very large. The conventional condensation systems, for example, require as make-up water normally 1 to 2%, based on the mass flow circulating in total, of the steam/condensate circulation. In combined cycle systems embodying steam injection to reduce the emission of nitrogen oxides, this percentage rises to 15% and still higher.
Another important case is represented by those systems which produce process steam. The condensate flowing back from heat exchangers, reactors, heaters etc. generally contains large amounts of dissolved air since the condensate has frequently come into contact with air in open channels and storage tanks. In not a few cases, even rainwater is also added.
The conventional degasser--as a rule combined with storage tanks--is little suited for achieving this object.
2. Discussion of Background
Known in connection with the degassing of liquids are exchange towers, also termed columns (LUEGER, volume 16, Lexikon der Verfahrenstechnik [Lexicon of Process Engineering], fourth edition, Deutsche Verlags-Anstalt, Stuttgart, page 51). These are as a rule cylindrical tubes in which the steam and the liquid of a mixture are fed to one another in countercurrent or in cross-countercurrent. Inter alia, so-called packing body columns, which contain packing bodies deposited regularly or irregularly inside the tower jacket are used. In these, the liquid and the steam of a mixture to be separated are fed to one another in countercurrent in a manner such that both phases make as intimate contact as possible with each other for the purpose of mass transfer and for the purpose of heat exchange.
The use of a packing body tower connected in countercurrent is in principle correct--for the purpose of achieving a maximum separative work at a particular packing body height. However, with a countercurrent connection, the presence of a fairly large supercooling entails the problem that a very large proportion of the steam has to surmount the lower part of the tower (flooding of the packing) without significant effect for the substance-kinetic separative work which occurs in the lower part of the tower since the condensate heating and saturation process take place in practice in the upper part. The consequence of such a design solution is, however, that the diameter of the tower has to be very large to prevent flooding of the packing, with appreciable additional costs for the apparatus.